The objectives of CA-10729-07 remain essentially the same as they were in the original application. A spectrum of more than 40 transplantable hepatomas are maintained in vivo. The growth rate of these hepatomas differs by more than 20-fold. The time between transfers differs from two weeks for the fastest growing line to more than 12 months for the slowest growing line. Histologically the rapidly growing tumors are poorly differentiated. Most of the intermediate growth rate tumors are well differentiated and the slowest growing hepatomas are highly or intermediate between well and highly differentiated. This spectrum of tumors affords investigators many choices in determining the essential from the non-essential alterations which occur in the neoplastic transformation by examining many biochemical and biological parameters. Very accurate and detailed records are kept on every transfer generation from the primary tumor to the present. The growth rate for each "Pedigreed" tumor line remains stable over many transplant generations. None are identical. Our spectrum of transplantable hepatomas is the only large one available. The tumors grow satisfactorily only in the inbred rat strain of origin. This project is designed (1) to maintain a large pool of transplantable tumors to support collaborative studies, (2) to develop new transplantable tumors more like the tissue of origin, and (3) to help support a center of excellence in experimental cancer research in the Howard University College of Medicine.